I highly doubt in the few days Uber has been on the market the "public at large" has purchased any significant share of Uber using their pension accounts. It's not in an indices so they're certainly not exposed through that.
* Just an example I don't know if they bought into the IPO or not.
eg:
> CalSTRS has owned shares in Facebook, Inc. since its initial public offering in 2012, as well as through privately held assets prior to the IPO.
https://www.calstrs.com/statement/calstrs-ongoing-engagement...